Clock



FIG. 1 is a front, left-hand side, top perspective view of a clock comprising a new, original and ornamental design;

FIG. 2 is a front view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof.

Portions of the rear of the clock, not shown, form no part of the claimed design. 

CLAIM The ornamental design for a clock, as shown and described. 